Pete B
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Posts posted by Pete B
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Using the 5002 tweeters in OLA/NLA has been discussed here before. OLA has a 2nd order network
NLA 1st order but the 5002 has a 3rd order and it should be duplicated if you want to use the dome
tweeters. I don't think that the 5002 sounds as good as the OLA and would suggest going back to
the original tweeters.
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If you are up for it the Econowave Mod makes a lot of sense for your application. You
could use one waveguide tweeter with two woofers. I can explain it if you are interested.
If you don't want to do that, then the first question is what revision of the OLA are your
speakers? The first revision with the very light weight red dot inductors were known
to have the wire burn up and possibly short out. There was a tech note from Advent
about measuring the DCR of the inductor when replacing tweeters. I would just replace
the tweeter inductors with 18 or 20 ga air core if you have the dot type inductors.
Some of the tweeter resistors are near the switch and they were probably the source
of heat.
I've been writing this assuming you want to use them as PA speakers, are the Peavy s good
enough so that the Advents are going back to home use? I'll bet that the Advents had
better bass.
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Nice work!
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Poplar should be far easier than stapling into masonite or mdf, it should work fine.
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Is Poplar a Hardwood?
Written by Chris Deziel; Updated October 16, 2019Poplar is a hardwood, but it isn’t a hard wood. The most common species in the United States, yellow poplar (Liriodendron tulipifera), is found throughout the Northeast as well as in Canada, and it’s deciduous. The question may arise in your mind: “But is poplar wood strong?” and the answer is yes, but it isn’t as hard as most hardwoods, with a hardness rating less than that of some species of cedar, which is a softwood.
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I think .75" square poplar cut with the bevel might look better being less bulky looking than Glen's.
But of course measure first to be sure that everything fits and clears.
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Power ratings with speaker drivers are mostly wishful thinking. It is really very simple a 1" voice coil
wound on an aluminum former typical of a tweeter is most often good for about 10W RMS perhaps
15W with ferro fluid due to thermal heating. The average power in music is much lower than the peak
so many companies rate in system "Music" power. It is all a ratings game.
The other limit is displacement at the lower end of the spectrum for the driver, you want tinsel lead in
wires with a tweeter that is driven hard at the lower end of the spectrum and an overall "good" design
so that the wires do not break. You have determined that the Advent Tweeter fails under your use
condition, might as well try the Q1R and let us know how it goes.
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That AR-3a Improved crossover is nearly the same as the AR-11 with the noted use of
Lpads except for the tweeter cap going from 10 uF in the AR-11 to 4 uF. I would probably
experiment with 6 to 8 uF when using the AR-11 tweeter. I measured some peaking in the
stock AR-11 tweeter crossover section with the 10 uF and the level full up. I'd have to check
my notes on the measured crossover frequency.
I would not go larger that 4 uF with the older non-ferrofluid tweeter in the 3a.
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Here's a picture:
1. remove the strap on the red terminals.
2. loosen the screw caps for both red and the top (mid/tweeter) black.
3. connect the 4 ohm from lower red to top red.
4. connect the 10uF from the lower red to the top red.
5. connect the 20 ohm from the top black to the top red.
6. connect the amp connection to the woofer input as shown.
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Check the foam on all the drivers and check to make sure that the mids and/or tweeters are not blown.
I'll try to take a picture of how to set it up when I have a minute.
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They are looking great! What is the thinking behind RAF then Watco over it, isn't Watco Danish Oil
also a colored finish? I have used it but not over RAF.
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Nice work, I'm very pleased that we have another alternative!
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Odd, given the AR interest here that L-Pad info comes in 4th and then 11th and lower for AR topics.
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Fixed it in the original post, seems to me the A40 _should_ have been called A35XL for the naming to be consistant.
There were also versions with dual woofers with pictures posted on here. The file name is A45 but I'm not sure if
that is correct:
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Interesting, first I've heard of these.
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I wrote if for our local audio club then thought why not here also.
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@TheFrugalAudiophile I've been building and designing speakers since I was a kid and I like to study the
classics to see if there are any "tricks" or design methods that are not mentioned in the literature. That is
my main reason for studying many of the vintage designs. My brother and I as teens read the stereo mags
and we debated with my dad about Dyna A-25 s, Large Advents, and we also heard KLH 6 s at the store.
We ended up with Advents because the store didn't have A-25 s and they seemed like the best deal.
I was given a pair of A-25 s in college in need of repair so I know them fairly well but I bought this pair
in order to measure an "Aperiodic" design which I have not yet done other than to read the literature on it.
My current view is that they wanted to "cram" that 10" woofer into the smallest box possible which if
sealed would have led to a high Fc and High Qtc. The lossy leak lowers the Q but does not really help
bass response. It is a non-optimal design IMO. What the A-25 really wants is a much larger box 2 -3 cu ft
tuned to 35 Hz with a moderate amount of internal damping. It also needs a modern tweeter.
The DeVore Orangutan supports this theory - note that they are tuned to 43 Hz for strong bass for
Low E on a bass guitar in the still too small box:
https://www.stereophile.com/content/devore-fidelity-orangutan-o96-loudspeaker
The A-25 is a very old design and it shows, as are many vintage speakers, both the woofer and tweeter
have paper voice coil formers providing very limited thermal capacity. The OLA in contrast has a strong
bronze former that will take massive power. Tweeters usually have paper thin aluminum VC formers.
The A-25XL has a newer version of the woofer with an aluminum former and a stronger ceramic magnet,
many say that they do not sound as good probably because the stronger magnet removes some of the
built in baffle step and some contouring of the woofer's response is needed to compensate.
The A-25 has a 1.5" tweeter that has very limited output above 12 KHz. A-25s sound reasonably well
balanced even though there is no crossover on the woofer probably as a result of the high VC inducance
acting to shape the response. I've never bothered to measure the A-25 frequency response or seen one
published, but they sound so good that I've always been suspicious of a depression, perhaps large,
around 2 KHz. Sure enough, I found a magazine published response and it was there. It also showed
the steep roll-off in the bass around 75 Hz. I started a thread here with some history and links to the
articles on the A-25, one with frequency response curves:
There are 10 dB dips in the frequency response on axis but they go away slightly off axis, so if you
position your speakers right it is possible to get a much smoother response.
Even with all the negatives about Dyna A-25 s you can get a really nice balanced sound due to them
having a tweeter level control and in the right position a smooth midrange. Leaving a bit of the
midrange notch can make them "magical" because it seems to match well with what is needed from
2 speakers producing stereo in a home listening room. Just do not expect to Rock out at party levels
for hours on end. Use them with a 50 to 100W max amp being very careful on the level and use the
power just for peaks.
I once started a thread on the Stereophile Forum "When Bad is Good" to discuss how sometimes
theoretically correct is not "best" in a home listening space.
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The leaky bass vent is described as aperiodic by Dynaco and here is an old
article on the concept:Here is a post on aperiodic venting by Richard Pierce from 1994 on rec.audio.highendthe action and reality of a variovent can be accurately modeled using a standard
vented model (4th order) with the following adjustments:
1. Since the vent diameter is relatively large and the vent length
essentially the thickness of the panel it's mounted in, the actual
vent mass is quite low, that results in a box resonance which is
much higher than would be considered reasonable for a vented system,
which means that a system aligned with such a port would indeed have
a very strange response, if it were not for the fact that:
2. With the damping in the vent, the port losses are extremely high,
the resulting Qp is VERY low (around 1-2 max), and thus the action
of the port at box resonance (at the high frequency it has) is
significantly attenuated to the point where the contribution to the
system's total volume velocity is essentially attenuated to
insignificance.
The result is a vented system with a high Fb that has a very low Qb. Such
systems, while still technically 4th order, approach 2nd order behaviour
at and below resonance for a significant range.
What advantage does this have? Well, with normal woofers, it's not clear.
It has no efficiency advantage over properly designed closed boxes, it
does not have the bandwidth or efficiency advantages of lower-loss vented
systems. It might have an advantage when you are forced to use a
high-resonance, high Qts woofer (just like some of the woofers Dynaudio
makes, for example).
But, magic it is not.
--
| Dick Pierce |
| Loudspeaker and Software Consulting |
| 17 Sartelle Street Pepperell, MA 01463 |
| (508) 433-9183 (Voice and FAX) | -
This page provides some background about how Dynaco was started in 1955:
I've not found much written about how Dynaco got started producing speakers and I'm
going to emphasize the A-25 here.
Greg Dunn had a page on Dynaco but it is now only available in a .pdf.The vast majority of Dynaco speakers used high quality drivers from SEAS,however there was an early production run of the A-25 that employed ScanSpeak drivers. The Scan version is easy to spot having the vent on the toprather than the bottom.Dyna produced 4 main models, all 2-way, that were imported into the US:A-10 very small mini monitor sized speakerA-25 $79 each, medium sized bookshelf, vented aperiodic designA-35 large sized bookshelf, sealed aperiodic designA-50 very large "bookshelf", sealed aperiodic designThere are reports of an A-40 and perhaps a few others but they are very rare.All of the above systems employed drivers with ALNICO magnets and papervoice coil formers resulting in limited power handling. The XL series employeddrivers with aluminum VC formers and stronger ceramic magnets. I'm onlyaware of the A-25XL and A-40 versions. The stronger magnets made themabout 3 dB more efficient and the aluminum former more resistant to thermalfailure.I had never seen a test report with frequency response measurements untilrecently. Here is a .pdf with reviews of many Dynaco products and 3 of theDynaco A-25:from this page toward the bottom: https://www.updatemydynaco.com/#DynacoCatalog1975Note that one of the reviews has frequency response curves and the on axiscurve is not very good having two glaring 10 dB dips in the midrange, howeverthe 30 degree to the left or down correct the problem. The speakers shouldsound much better upside down placed low or facing forward but to the left of on axis.It is also interesting to note from the frequency response curve that the bassresponse drops like a rock below 75 Hz. The rolloff is 4th order 24 dB/octbecause they are a vented system. Some incorrectly claim a gentler roll-off foropen Aperiodic systems but they would be wrong. Some reviewers claimed thatthe A-25 will produce 30 Hz bass but that would be wishful thinking or mostlydistortion.The normal production runs of A-25 s were not "mirrored" with most having thetweeter a few inches right of center. Oddly, my pair of A-25 s ARE mirrored soleft toward center of the right speaker, and right of the left speaker should havemuch better frequency response.It seems that the tweeter needs to be further away and therefore tilting themback should also work for pairs that are not mirrored.I restored my A-25s by refinishing the boxes, recapping with Clarity 5 uF capsthat are within 2% of the design value, adding gold binding posts and machinescrews to mount the drivers. Tested the resistors for spec value and cleanedthe selector switch contacts with Deoxit. Note that they are mirrored by probablycoming from different production runs. -
On 12/30/2019 at 2:16 PM, Vicious-Poodle said:
Hello, Martin. I'm surprised that you like the EPI 100 given your praise of Dynaco speakers (not that I don't admire the restoration done here, great work) but these were really highly reviewed by Consumers Reports. I remember rude high pressure sales people, now out of business decades later, they denigrated the Dynaco A25 they had to demo against, along with the AR-2AX.
Personally, I found them too bright (didn't an AR designer say "Who would want to listen to a flat to 20KH speaker?) and monochromatic: I couldn't hear details I heard on the USS driver Dynaco, differences between recording studios and techniques, voices weren't as pleasant, etc.
In fact, probably a better cheaper choice now is this much hyped Elac Debut, not as bright to me as EPI 100.
https://audioplacebo.com/elac-debut-2-0-b6-2-review/
I'm using Emotiva UMC-200 for digital sources, and changed to Emotiva BasX amplifiers, the Chesky demo disk is heart breaking because their recording techniques leave the big labels in the shade, I wish so many great singers and performers had engineers with their talents.
https://www.amazon.com/Ultimate-Demonstration-Disc-Critical-Listening/dp/B00002MXUH
Anyway, I wish you all a Happy New Year. I think the retro speakers might outperform in musicality many of these modern offerings but I wasn't fond of EPI. Not as bullet proof as the Dynacos. Foam surrounds, etc. And that harsh character I noted. Accuracy is more than "flat" response, IMHO.
My interest in the EPI 100 s started with my brother mentioning that they were recommended by Stereophile,
back when they first came out, I also read very positive reviews in the magazines.
I think it was a C or D ranking but at least they got a recommendation. I went out to listen to them and they
did indeed sound very good. Their strengths are deep bass roughly to the mid 40s, smooth midrange, and
a clean extended high end to at least 15 KHz if not 18. On top of it all they sound VERY good and real, like
music in the room.
Note that there is a version with a tweeter level control and others without, I would always add the level
control because they sound best with about 3 ohms in series with the tweeter. Yes, they are bright without
the control but there is a simple solution get the correct version or add the level control.
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Hi, Yes sure if I have room I'll bring them.
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I remember looking at Ken's mod but I have very little memory of it, I think it was simple perhaps
film caps but that is just a guess.
@kavalski Do you have OLA or NLA s and how many watts?
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The original thread for this is here at AudioKarma with impressive pictures of the new place:
It’s time to get psyched up for will promise to be our must epic event yet!
Thanks to Bill aka SpikeDart who found us the site and is our local liaison.
We are renting the Masonic Lodge - which is a converted church - This location will only be a few minutes further for folks driving from the masspike.
Address:
12 Church Street
West Boylston, MA 01583
We have the facility all day so the doors will be open at 10 AM for setup and we’ll wrap it all up by 5PM.
Obviously, we’ll be asking people to stay and clean up any mess - we want to be invited back!
This is a much larger an nicer space than what we’ve been using most recently in Sutton and it has a variety of areas that can be used for selling and auditioning systems.
Admission will be once again be a paltry $5 each - if you’re bringing along disinterested people they’ll be free - but anything you can contribute will certainly be appreciated.
You should enter through the front door and pay your admission fee after which you can use the side doors to bring in treasures for sale in the lower level function room.
T shirts and sweatshirt orders will be available for pick up just inside the front door as well.
There is parking in the side lot, on the street and in the field behind the building.
The upper level auditorium area will be used for auditioning systems.
There is also a medium sized and smaller side room that can be used for auditioning systems.
The lower level will be used for selling and there’s a kitchen area.
There are a limited number of tables - if you partake of them only take one - if you can you should bring your own as well.
There are a limited number of power outlets - if you need power for a system bring extra extension cords and power strips.
Everyone should bring some appropriate snacks/drinks. Alcohol should be OK in moderation - but this hasn’t been an issue in the past and most of us are driving a fair distance so it’s best to watch your consumption.
Of course no smoking inside the facility.
I will post a Barter Town thread in about a week and link it here. -
deleted
Smoking Advents
in Advent
Posted
http://baselaudiolab.com/ADVENT_LA_XO.html
Figure 5 has the schematic.